k&r-cat-v2.c

#include <stdio.h>

/* cat: concatenate files, version 2 */
main(int argc, char *argv[]) {
	FILE *fp;
	void filecopy(FILE *, FILE *);
	char *prog = argv[0];  /* program name for errors */
	
	if (argc == 1 ) { /* no args; copy standard input */
		filecopy(stdin, stdout);
	} else {
		while (--argc > 0) {
			if ((fp = fopen(*++argv, "r")) == NULL) {
				fprintf(stderr, "%s: can’t open %s\n",
				        prog, *argv);
				exit(1);
			} else {
				filecopy(fp, stdout);
				fclose(fp);
			}
		}
	}
	if (ferror(stdout)) {
		fprintf(stderr, "%s: error writing stdout\n", prog);
		exit(2);
	}
	exit(0);
}